With the developments in technology, it has been springing up recently of portable electronic products, in particular, it has been favouring for people to use portable electronic products with camera function. As for a conventional optical system, a photosensitive element therein may be anything other than a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). Along with improvements in the technology of semiconductor manufacturing process, the photosensitive component is of a reduced-size of pixel. Accordingly, the camera lens assembly of the optical system is required to be smaller, so as to facilitate the miniaturization. In addition, the imaging quality of the camera lens assembly is further improved in need, so as to match the photosensitive element.